Impulse means for rotating ammunition projectiles at low speeds



RAMEY ROTATING AMMUNIT United States Patent i States of America4 asrepresentedbyy the 'Secretary of theArmy Application February 28'; 195%,Serial No. 274,0461 4 Claims.. (ciauz- 511).

(Granted. under Title 35, U. S; Code (1952), sec. 266) 'Eher invention.described: herein4v mayE be manufactured and! useidf by on for? thefGovernment. for governmental purposes without the payment of; any`royalty thereon.`

Recent. developmentsv in the' military weapon: and ammunition art. have'led to,` the use. of what: has; been termed. the` shaped chargez, Thistype; ofi` projectile, amongyothers, requires a very'minimum. amount oflspin while` in. flight, as' tooy much spin has. been. known to spoilrits armor-piercingor other suchl desired: characterist-ies.. O11y the:other hand,. some1 small amount of. spin isnecessary in order tooiitset. the.` norm-al lack of sym.- metry' in` the manufactured`partsi.. In. thei case of"` the gun and ammunition hereint illustrated.(Eig. 1);. a1' recoilless; firing device similar to that' shown byfKro'eger- Musser UI S. Patents 2,466,714 and 2,472,111. but ernploying amore; recent. type. of` projectile: which is; iinstabili'zed,. it hasbeen. determined; that ai suitable: com'- promise: between: these:twdfrequirements is' orr. the: order of: lll-20` revolutions; per:secondi.

Broadly stated, therefore,A it is: the principal objectief my inventiontot provide a. means for imparting acontrolled,low'rotative speedltoprojectiles` fredzzfromzat gun ried forrnormal.. spin stabilization of;theprojectile.'`

Another: object.' is; to.-` accomplish?. such'. rneansfiir au fast,economical; manner with; a; minimuma amount. of". altera;- tion being;required': fon the. ammunition and. noneffor the1 gun.

These and other: related objects are accomplishedi bty my finventionzvasrwill be seen; by referencer:tofthefollowingj specification: andl the;annexed drawingsg. wherein:

Fig.. l shows portions offazbarrekand breechgin longitudinal: section,of: a'. rifled reeoillesss gum. together with a planview. offanammunitionround' Whose projectiles outerfwall is. knurledz to:`etfectr at low' speed spirn im ac.- cordanceI with. my invention;

Fig. 2 depicts anenlargedpiortion: of the'knur1ingl on thei projectileand.` the=.opposed` barrel: riing-:asx selen: from line 2.-`-2.of Fig:1;:

Fig; 3 is a much enlarged; illustratiom thei knurled projectile portion(as'zshowrr in Fig; 11),; on; whichhas been super-imposed thee bands ofthesrified gun; barrel just-as'if'the view was: through thegunsineariwallwhich has been removed; and

Fig; 4 is a` view of theknurled1projectile.:portiomsimilar to that shownin Fig: 1i except: that' thezknurlingf is on` the-forward portion.offthexbourrelet proper, rather than just` ahead of 1 the f bo'urrelet`as: in'r theeEig. 1 representation.

Prior` art means: fory spin-inducing projectile'sgenerally have reliedupon mechanical.;V engagement between'. the borey of the gun tubeandtheprojectile; Thiszwas genL erallyf accomplished. by 'helicallyrrillingl the?. gun. barrel (as-at-9`1'0 in Fig'. 1)., andi providingarounditheprojectilea rotating band which.wasrelatively'soft.andcut itsteethand. grooves inf traversing the rid ba'rre'lf.v or else-waspreeng-raved.` to mesh with the riiling's:4 Suc-h spin-inducing means,`howeven. invariably rotated". the

ratented oet. 16,. 195s projectile ata far faster speed than thelll-'26' R.: S. limitation above mentioned. By comparison, from thedrawings and the following description it will. be noted thatfI haveaccomplished the aforementioned objects by uniquely knurling, milling,shaping or broaching grooves in. the projectilefs` outer wall to allowpropellent gas to stream. thereinto and' thus cause the projectile tospin for. reasons whichwill be explainedk below; In. this way, thetremendous energy of the propellent gases used to place the projectilein flight is likewise employed to do 'the' j'ob of spinning theprojectile. Since some off the gases which" evolve when the ammunitionis tired will course through the length of. the barrel. between thepro.- jectile and the barrel wall andA in. the grooves. of'.v` theriings in the gun tubes, those` gases are allowedlto eX- p'and" intothe. grooves on the projectile wall'. andexert rotative force againstthe teeth-like walls thereof.

For a better understanding of' my invention. the various components.shown in the drawings will` now be identied and theii functions Brieflydescribed. The conventional gun shown is of' a recoillesstype (althoughobviously my invent'onneed not be. limited to use with such guns), of"which a barrel 8,. having riing lands. 9 and"` grooves. lll', and arearwardly expanding. chamber 11 are. illustrated-.` The ammunitionround consists of a projectile 1`2` having. a rearward extension. 13which nestsinside; a cartridge case 1141 Extension 13-opti`onal ly.'bears.- a number. of flight-stabilizing fins 15l (only one i`s shown).Propellent. powder' 16 surrounds the projectile extension. Although' theillustrated ammunition is of. aspecial form toWhichrny invention neednnot be limited; it has been selected as an example primarily because. itrepresents a type which happens. tobe most effective when its projectileis given a minimum. spin, and-.therefore my improvements arel ideally;suited theret0.

The projectileis provided with a bourrelet 20 which is the largest.diameteredportion of the projectile and th11si`n. well-known. manner,serves as the riding surface which contacts lands 9 in moving forwardlythrough the. barrel; In addition. thereto, the bourrel'et normallyserves as, a Barrier to prevent' the forward escape of gasesexceptforthose g-aseswhich escape-therepast especially through. therillinggrooves ofthe barrel. On the forwardy portion or. end 7 of` thebourrelet' (as in Fig. 4)., or on a lesser diametered region justforward. of the rearward or uniform diametered portion of lthe bourrelet(as shownin.. Fig.. l) torque-inducing means comprisinga. plurality ofvteeth 22 and slots 23' are cutv hy any suitable" means suchy -as aknurling, gear hobjbing gear shaping, or broaching machine. The anglemee. Fig. 3)f between. these teeth andthe aXil'center-line of`theprojectile may be varied] depending. upon the amount of projectile spindesired, the weight of the projectile to be. spun, the force to besupplied-byva particular propellentpowder, the ballistic relationship ofthe projectilev to the gun,. etc. This angle may' be determined quitereadily either by calculation or empirically, as desired.V Thus,.thetorque-inducing teeth or' slots areeac'h disposed'alonga line.whi'chforms an acute angle with or. within.an imaginary planewhicli isinclined' with' respectto the axil center-line of the projectile b'utwhich is inclined' in an opposite sense ascomparedlwith` theinclination.; of.y theimaginary planes. including the guns riing landswith respect. to: the gunsv arial` center-line.

The operation: of;my invention should, byV now,.be apparent. Theforwardly moving gases evolved-upon ignition of propellent powder 16will be caused' by the gunislandslQ-tdow" (as'indicated/by arrow 26in1Eig. 3) throughzzgroovese I0 along ra; line whichsformsvthesa'n; gleat:withrthe'. projectiles arri-all` center-line.l When: the

thus directionalized gases strike teeth 22 on the projectile wall theywill be redirected thereby and move in a direction following slots 23(as indicated by arrow 27 in Fig. 3). Although this deflection may notbe imparted to all the gases immediately upon contacting teeth 22, bythe time the gas passes over the toothed portion 22-23 of the projectilean adequate portion thereof will have had its direction and momentumchanged.

This result, which can best be explained by reference to Fig. 2, isobtained by the propellent gases owing along riing grooves 10 overbourrelet 2i), which has been supplied (dotted lines) in Fig. 2, and thetoothed portion 2223 of the projectile. Before the gases reach thetoothed portion, in passing over the bourrelet they occupy only thespace in the rifling grooves indicated by A; then they are led into thespace represented as B. This increase in volume of passage caused bygrooves 23 allows the gas to expand and increase its velocity. Thedirection of the grooves on the projectile is such that the direction offlow of part of the gas is changed by an angle equal to +0 (from Fig.3), and continues to ilow in this new direction.

The principle of the conservation of momentum requires that when a masshas its direction changed there is a resultant force. The changing ofdirection of that part of the propellent gas that ows into grooves 23 onthe projectile surface causes a resultant force to strike teeth 22 whichact like so many turbine blades and produce a torque-inducing effectthereby causing the projectile to spin. The angular rotation of theprojectile will be in a clockwise direction as viewed from Fig. 2.Rotation in the opposite direction can, of course, be accomplished byslanting teeth 22 and grooves 23 in the opposite direction to thatshown.

As will be evident, my invention can be adapted to many types ofprojectiles for use in various types of guns with very little andinexpensive alteration to ammunition rounds being required, and nochange at all needed in the guns. The milling, knurling or other cuttingof the teeth and slots in the projectile wall can be done very readilyand inexpensively and, because the depth of slots or height of the teethneed be so relatively small, the projectiles in most cases will need noredesigning to provide adequate wall thicknesses therefor. pulsion forceis adequately supplied by gases that normally leak past the bourrelet,no additional powder will be required. Ballistically, the addition of myimprovement has been found to cause no change inthe ammunitionsperformance characteristics other than to give the projectile spins onthe order of l to 20 R. P. S., as

required.

It will therefore be noted that by my invention an effective means hasbeen provided for imparting a controlled, low rotative speed toprojectiles fired from a rifled gun, and this means can be accomplishedin a fast, economical manner with a minimum amount of alteration beingrequired for otherwise conventional ammunition, and none for the gun.Thus, one and the same rifled weapon is capable of ring projectilesrotated slowly by my herein described novel means, or rotated at muchhigher speeds by such prior art devices as mechanical engagement ofrotating bands with gun barrel riiings, etc. This, of course, makes itpossible for a gunner to put his weapon to dual usage-an invaluableasset in the field-without requiring diiferent guns or specialmodifications thereof to fire projectiles at differing rotative speeds.

My invention will likewise be recognized as extensive in its adaptationand is not to be restricted to the specific form here shown anddescribed by way of illustration.

I claim:

l. In an ammunition projectile to be red from a ried gun barrel, meansfor rotating the projectile at low speeds so as to offset the normallack of, symmetry of Since the proits components, comprising, abourrelet which is circumferentially located on the projectile betweenits forward and rearward extremities and whose external diameter forms acylindrical surface of substantially uniform diameter, said bourreletsurface including a forward portion and a rearward portion, each saidportion being adapted to slidably lit with the internal diameter of thegun barrels rifling lands, said forward portion being grooved to providetorque-inducing vanes each of which is disposed within an imaginaryplane which is similarly inclined with respect to the axial center-lineof the projectile but which is inclined in an opposite sense as comparedwith the inclination of the imaginary planes including the guns riinglands with respect to the guns axial center-line and within which theprojectile is to be used, whereby some of the gases used to propel theprojectile from the gun barrel will flow along the barrels riilinggrooves and over the projectiles bourrelet to impinge against thetorque-inducing vanes so as to minimize normal rotation of theprojectile otherwise imparted thereto by the riiled gun barrel.

2. In an ammunition projectile to be fired from a riiled gun barrel,means for imparting low-speed spin to the projectile so as to offset thenormal lack of symmetry of its components, comprising a bourrelet whichis circumferentially located on the projectile and whose externaldiameter form a cylindrical surface of substantially uniform diameter,said bourrelet surface including a forward portion and an adjoiningrearward portion, each said portion being adapted to slidably fit withthe internal diameter of the gun barrels riing lands, said forwardportion having a plurality of slots in the surface thereof to provideribs each of which is disposed Within an imaginary plane which issimilarly inclined with respect to the axial center-line of theprojectile, the inclination thereof being disposed in an opposite senseas compared with the inclination of the imaginary planes including theguns rifling lands with respect to the guns axial center-line, wherebythe gases used to propel the projectile from the gun barrel will ilowalong the barrels riiing grooves and over said rearward portion of theprojectiles bourrelet and out through said slots so as to minimizenormal lrotation of the projectile otherwise imparted thereto by therifled gun barrel.

3. A device for imparting low-speed of rotation to a projectile to befired from a rifled gun barrel, comprising a forward portion and anadjoining rearward portion located on the cylindrical outer surface ofthe projectile, each said portion being adapted to slidably engage theinternal diameter of the gun barrels rifling lands, said forward portionbeing grooved to provide a plurality of radially extending,torque-inducing teeth disposed on a line which forms an acute angle andinclined with respect to the axial center-line of the projectile, theinclination thereof being disposed in an opposite sense to theinclination of the guns rifling lands with respect to the guns axialcenter-line, said rearward portion comprising barrier means adapted forclose engagement with the guns rifiing lands to prevent the gases usedto propel the projectile from owing therepast except substantially thosegases travelling through the barrels riing grooves whereby such gases asdo flow therepast Will expand against said torque-inducing teeth toprovide an impulse for minimizing normal rotation of the projectileotherwise imparted thereto by the ried gun barrel.

4. In an ammunition round for use with a rified gun barrel, a projectilehaving a maximum diametered portion thereof comprising barrier meansdimensioned for slidably fitting the bore ofthe riled gun barrel forsubstantially preventing the forward escape of gases used to propel theprojectile from flowing therepast except those gases travelling throughthe barrels rifling grooves, the forwardly disposed portion of saidbarrier means comprising a plurality of turbine-like bladescircumferential- References Cited in the le of this patent UNITED STATESPATENTS Gleason Nov. 9,

FOREIGN PATENTS Austria Oct. 11,

Germany May 28,

Germany Feb. 18,

